1. Field of the Invention
The present invention relates to a carrier for spectroscopy and method of manufacturing the same and, more particularly, to a carrier for Raman spectroscopy.
2. Description of Related Art
Raman scattering is widely used for detection. When a molecular is excited by a photon to become vibrating or rotating, a portion of the photon energy is absorbed by the molecule leaving the scattered photon with less energy than it originally has. The amount of energy loss by the photon is determined by modes of vibration such as stretching or bending as well as the specific vibration energy. Because molecules of different structures and compositions exhibit different modes and energy of vibration, spectra representing energy of scattered photons after the incident photons of the same original energy have suffered from different amounts of energy losses can be used to distinguish a specific molecule from others. The energy losses are usually presented as a series of increased wavelengths from the original wavelength of incident photons. For convenience, changes in wavenumber instead of wavelength are shown as Raman shift. The aforementioned process results in scattered light with frequency different from the incident light. The frequency variation corresponding to the change of vibration energy is “Raman scattering”, and the spectrum of the scattered light presented as the changes in wavenumbers between the incident light and scattered light is “Raman spectrum”. Moreover, the difference in frequency, wavelength, or wavenumber between incident light and scattered light is “Raman shift”.
Since Ramen shift corresponds to the increase in rotational or vibrational energy of a molecule rather than the frequency of the exciting light, the Raman shift features of different molecules or structures can be applied for detection, identification, and quantification of molecular structures.
Surface enhanced Raman scattering (SERS) is known as one of the most sensitive modern Raman spectroscopy techniques. The principle of SERS can be briefly explained by the following example. When two or more inert metal nanoparticles are close to each other and exposed to appropriate light, the electromagnetic fields of the incident light cause free electrons in metal nanoparticles to move in a direction opposite to the local electric field resulting in separate accumulation of positive and negative charges on opposite sides of a metal nanoparticles and on the neighboring sides of two near-by metal nanoparticles. High density charges of opposite signs at a short distance from each other induce much stronger local electric fields than that of the incident light. Since electric field has positive correlation with the intensity of Raman scattering signal strength, the greater the strength of electric field generated from metal nanoparticles surface and adjacent particles, the greater the intensity of Raman signal is. Thereby, it can enhance detection sensitivity of Raman spectrum so as to make it a potential technology that can be used to detect various trace amount of a molecule in a short period of time. Also it can be widely applied in various technical fields such as biomolecule detection, drug testing, medical diagnosis, and analysis. In addition, as graphene film has excellent optical, electrical, and mechanical properties, it can be used to further improve Raman scattering spectroscopy, too.
In order to make SERS a useful sensor for real-life applications, more affordable and sensitive SERS substrates are desired. If a SERS substrate is made flexible, it can further extend the range of applicability of the excellent SERS molecular sensor. Therefore, less expensive processes than those commonly used for the fabrication of modern integrated circuit are widely sought after for the fabrication of properly located metal nanoparticles of desired sizes, shapes, and plasmonic properties for SERS applications.